Purple High School Graduation Caps. This purple graduation cap is perfect for your graduation ceremony and a perfect keepsake to treasure for years. Made from best quality tricot fabric the purple mortarboard cap measures 9.4"sq and designed to include elastic at headband for a 'one size fit all'. All high school graduation caps are offered by Gradshop at low prices, so order online and take advantage on huge savings for all graduation gap, gowns and tassels.